The present invention relates to a textile-cutting device, in particular for cutting and sealing textile tape, and more specifically with reference to an anvil construction for an ultrasonic cutting apparatus.
The use of ultrasonic energy for cutting and slitting textile material is well known. Textile cutters employing ultrasonic energy provide a sealed (welded/fused) edge as it is being cut, thereby preventing the unraveling of threads or the appearance of a frayed edge, and is thus preferred over conventional cutters in a host of applications.
Typically, an ultrasonic wave generator comprises a horn, which is vibrated by the generator against the peaked cutting edge of an anvil, thereby cutting a strip of material disposed therebetween. Such textile material is either thermoplastic or comprises a thermoplastic fiber content. As an example, in one such application, a roll of continuous printed labels is cut into individual labels using ultrasonic energy prior to stitching the cut labels onto garments. Optionally each label may be folded in two prior to being stitched to the garment, or, alternatively, the label strip may be folded just prior to the cutting operation such that as each label is cut, the upstream and downstream cut edges are fused together.
As the horn is vibrated against the anvil, for example at a frequency of about 30 to about 40 KHz, the horn undergoes at its output surface a small translation in peak-to-peak amplitude. At these conditions, large acceleration forces (typically of the order of several thousand g) are induced, and corresponding forces cause the horn, which is urged against the anvil, to be repetitively impacted and driven away from the anvil, thereby enabling a strip of material to be cut when disposed in-between the anvil and the horn. The anvil is thus subjected to severe vibration and impact forces, particularly on the edge thereof, which thus becomes worn rather quickly with use.
In prior art devices, the rapid wearing of the anvil has hitherto necessitated the anvil to be regularly replaced, a complex and costly procedure requiring the cutting apparatus to be disassembled and reassembled with a new anvil, with the ensuing down time and loss of production time, and associated costs including that of the new anvil.
It is therefore an aim of the present invention to provide a textile cutting device that overcomes or significantly reduces the limitations of prior art ultrasonic cutting devices.
It is also an aim of the present invention to provide an anvil construction comprising a cradle and a replaceable anvil lockable with respect thereto that enables the cradle to be mounted to the ultrasonic cutting apparatus, while allowing for simple replacement of the anvil whenever needed.
The present invention provides an anvil conduction comprising an anvil lockably mountable onto a cradle in one of at least two interchangeable mounting positions. Corresponding to each mounting position, the anvil has at least one longitudinal cutting edge and a corresponding engagement section for engagement with a complementary engagement means formed in the cradle.
According to the present invention there is provided an anvil assembly adapted for selective cooperation with a horn operatively connected to an ultrasonic wave generator such as to enable a textile workpiece disposed between said horn and said anvil assembly to be cut wit the cut and simultaneously sealed. The anvil assembly comprises an anvil and a cradle, said anvil adapted to be selectively mounted onto the cradle in any one of at least two mounting positions, wherein corresponding to each said mounting position said anvil comprises one peaked longitudinal cutting edge and a corresponding engagement section substantially parallel to a longitudinal axis of the anvil; said corresponding positioning and engagement section adapted for selective engagement with a complementary engagement means enabling said anvil assembly to be removably positioned and locked onto said cradle in a corresponding one of said at least two mounting positions such as to enable said peaked edge corresponding to said one of said at least two mounting positions to protrude from said cradle.
Typically, the engagement means comprise at least one abutment member which abuts the anvil against a complementary engaging surface of the cradle. The engagement surface may be in the form of a receptacle or a projection, formed of one or more wall portions, which together with the abutment member provide positioning and fixation means. Thus, the anvil may be easily positioned on the cradle without having to remove the cradle from the ultrasonic cutting apparatus, rendering replacement of the anvil assembly of the cutting apparatus a straightforward operation. The anvil itself may therefore be a simple component that is relatively inexpensive to manufacture.
In the preferred embodiment the anvil is in the form of an elongate prism-like member having a nominally constant transverse cross-sectional profile along its longitudinal axis, and comprising a plurality of longitudinal cutting edges, angularly spaced one from another with respect to the longitudinal axis of the anvil. The prism-like member is locked onto the cradle by means of said engagement means, in any one of a plurality of angular positions, the number of angular positions being correlated to the number of parallel edges of the prism such that in each position one cutting edge is in turn brought into registry with the horn of the ultrasonic generator. Thus, as one edge becomes worn and unusable, the prism is removed from the cradle, rotated about its axis and replaced in the cradle such that a new edge is aligned with the horn.
The anvil according to the present invention may also be designed for incorporation in a cradle that is retrofittable with respect to existing ultrasonic cutting machines.
Furthermore, it is also possible to double the useful life of the anvil by aligning the horn with one longitudinal half of the anvil, rather than the center section thereof. Thus, following the aforementioned procedure, only up to one half of each edge gets worn in turn. By removing the anvil from the cradle and turning it by 180xc2x0 about a vertical or horizontal plane comprising the axis of the anvil, the unused half of each edge may in turn be brought into registry with the horn.